nilfs2: add nilfs_get_folio()

Convert nilfs_get_page() to be a wrapper.
Also convert nilfs_check_page() to nilfs_check_folio().

Link: https://lkml.kernel.org/r/20231127143036.2425-10-konishi.ryusuke@gmail.com


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>